It is known to produce rotors of large turbomachines of steam or gas turbines by welding individual, processed disks together to form a unit. The procedure which is conventional in the prior art for producing a rotor is described, for example, in CH 595 011. According to this document, the rotor is assembled by joining individual disks together in a stepwise manner. In this process, two disks to be joined are initially pressed against each other, heated and then welded together. Then, the further disks are mounted step-by-step by repeating the three steps mentioned until the entire rotor is complete. All of the steps are carried out in a common heating apparatus. EP 0 604 754 A1 discloses a process for producing a turbine rotor from individual, standardized rotor parts, which have been produced so as to be parallel in relation to each other to minimize the final production steps.
All production systems for producing rotors by the known process described above have to be designed for the size of the end product. It is very expensive to construct such large fabrication devices since these are at the boundaries of that which is physically feasible and can be constructed only with high technical outlay. In addition, large fabrication devices are technically unsuitable and financially uneconomical for the production of small rotors. This disadvantage is also described in EP 0 604 754 A1. In order to meet the needs of the fickle market, the highest possible flexibility is required.
DE 23 24 388 explains that the production of a high-quality root seam in the case of a vertical rotor axis requires complicated and expensive welding processes, and that technical difficulties may arise, in addition to the uncontrollability, when assembling large rotors vertically. A further disadvantage addressed in DE 23 24 388 is that the rotor has to be transferred in the warmed state from the vertical position into the horizontal position by known processes, in which all disks are assembled in sequence in the vertical position of the rotor and welded together by root seams. DE 23 24 388 mentions the aim of simplifying the technological process, increasing labor productivity and reducing capital investment. In DE 23 24 388, these objects are achieved by assembling and welding the rotor in the horizontal position, such that no rearrangement is required after the assembly operation.
CH 595 011 describes the use of the TIG (Tungsten Inert Gas) welding process for joining one disk to the next in the horizontal direction, and the performance of a submerged arc welding (SAW) process for filling the remaining grooves. In this case, one disk is joined to the other in a step-by-step manner, followed by preheating, prewelding and finish-welding, before the next disk is attached axially in the horizontal direction and the procedures are repeated. This document explains that the size of the heating box has to be extended to the new length of the disk stack for the finish-welding after each prewelding operation, or has to be adapted to the rotor length which increases step-by-step, since all production steps are carried out in a common apparatus. CH 595 011 discloses that two additional disks may in each case be preheated and prewelded so that in each case two grooves can then be filled simultaneously by the submerged arc welding process, since the submerged arc welding process lasts for a very long time. The size of the heating box could thus be expanded in each case by two elements in one go. At the end, after all the disks have been welded on in a step-by-step manner, the rotor is subjected to a stress relief annealing process and then ultrasonic testing.